Systemic Therapy for Stage I-III Anal Squamous Cell Carcinoma Guideline

Dr. Van Morris presents the new evidence-based guideline on systemic therapy for localized anal squamous cell carcinoma. Dr. Morris discusses the key recommendations from the Expert Panel, including recommended radiosensitizing chemotherapy agents, dosing and schedule recommendations, the role of induction chemotherapy and ongoing adjuvant chemotherapy, and considerations for special populations. He emphasizes the importance of this first guideline from ASCO on anal squamous cell carcinoma for both clinicians and patients with stage I-III anal cancer, and ongoing research the panel is looking to for the future.

Read the full guideline, “Systemic Therapy for Stage I-III Anal Squamous Cell Carcinoma: ASCO Guideline” at www.asco.org/gastrointestinal-cancer-guidelines.

TRANSCRIPT

This guideline, clinical tools, and resources are available at http://www.asco.org/gastrointestinal-cancer-guidelines. Read the full text of the guideline and review authors’ disclosures of potential conflicts of interest in the Journal of Clinical Oncology, https://ascopubs.org/doi/10.1200/JCO-24-02120

Brittany Harvey: Hello and welcome to the ASCO Guidelines podcast, one of ASCO's podcasts, delivering timely information to keep you up to date on the latest changes, challenges and advances in oncology. You can find all the shows, including this one at asco.org/podcasts.

My name is Brittany Harvey and today I'm interviewing Dr. Van Morris from MD Anderson Cancer Center, co-chair on “Systemic Therapy for Stage I-III Anal Squamous Cell Carcinoma: ASCO Guideline.”

Thank you for being here today, Dr. Morris.

Dr. Van Morris: Thank you for having me. On behalf of our committee who put together the guidelines, I'm really excited to be here and talk with you today.

Brittany Harvey: Great. Then, before we discuss this guideline, I'd like to note that ASCO takes great care in the development of its guidelines and ensuring that the ASCO Conflict of Interest Policy is followed for each guideline. The disclosures of potential conflicts of interest for the guideline panel, including Dr. Morris, who has joined us here today, are available online with the publication of the guideline in the Journal of Clinical Oncology, which is linked in the show notes.

So then, to jump into the content of this guideline, Dr. Morris, can you provide an overview of both the purpose and the scope of this guideline on stage I to III anal squamous cell carcinoma?

Dr. Van Morris: So anal cancer is considered a rare malignancy for patients in the United States and across the world as well. Even though it's not something we see as commonly, for example, as the adjacent colorectal cancer, this still is a cancer that is rising in incidence every year in the United States. And really, despite the presence of the preventative HPV vaccines, which we hope will ultimately prevent and eradicate this cancer, we still expect the incidence to continue to rise in the coming decades before we really start seeing numbers begin to decrease as a result of the vaccine. So this is an alarming trend for which oncologists will continue to see likely more and more cases and new diagnoses every year. So we wanted to review the most recent literature and provide oncologists up to date recommendations for how they can best take care of patients with a new diagnosis of localized anal cancer.

Brittany Harvey: Absolutely. I appreciate that background and context to set the stage for this guideline.

So then next I'd like to review the key recommendations of this guideline. So starting from the first clinical question, what are the recommended radiosensitizing, doublet or single chemotherapy agents for patients with stage I to III anal cancer?

Dr. Van Morris: It's true that really the standard treatment for patients with localized anal cancer has not changed over the last literally half century. When the Nigro regimen was first reported back in 1974, 50 years ago, the standard of care for patients with a new diagnosis of localized anal cancer centers around concurrent chemotherapy and radiotherapy. And we looked at the various randomized control trials and the highest level of evidence which has been reported over the past decades, and really for most patients, the standard of care continues to remain doublet cytotoxic chemotherapy in combination with radiation. We reported that the most commonly, and I think most accepted, regimen here is a combination regimen of 5-FU, intravenous 5-fluorouracil with mitomycin C. And this most commonly is given on a week 1 to 5 regimen. The 5-FU, we recommended a dose of 1000 milligrams per meter squared per day on days 1 to 4 and then on days 29 to 32 of the radiation treatment. And then the mitomycin C, looking at various trials, has been given at a dose of 10 milligrams per meter squared on day 1 and day 29, or alternatively a single dose of mitomycin C at 12 milligrams per meter squared on day 1.

I think that the thing that's important for clinicians and patients alike to remember is that this chemotherapy can be very toxic in patients who are undergoing a curative-intent therapy for this diagnosis of localized anal cancer. I think it's just important for oncologists to be watching closely the blood counts for the patients to make sure that the myelosuppression doesn't get too bad. And then in select cases, if that is the case, when the oncologist opts to go for the day 1 and day 29 dosing, it may be prudent, if the myelosuppression is too excessive, to consider withholding that day 29 dose.

Brittany Harvey: Great. Thank you for providing those recommendations along with some of those dosing and the schedule recommendations from the expert panel.

So are there any other alternate dose or schedule recommendations from the expert panel?

Dr. Van Morris: Yeah, but I think that we saw with the ACT II data that was a randomized trial that was done out of the UK that compared 5-FU mitomycin with 5-FU cisplatin as two different doublet cytotoxic regimens, that overall outcomes were very similar between the two regimens in terms of curative outcomes for patients treated whether 5-FU mitomycin or 5-FU cisplatin. So certainly there is evidence supporting the use of cisplatin as a second cytotoxic agent with 5-fluorouracil. In the ACT II study that was given at a dose of 60 milligrams per meter squared on days 1 and 29 along with the 5-FU at the regimen I talked about previously. There is other lower level of evidence data suggesting that even the 5-FU and cisplatin can be given on a weekly schedule and that that can be safe. Actually, at my institution at MD Anderson, that is our standard practice pattern as well.

There's also the option when we're thinking about giving pelvic radiation for patients with lower GI cancers, many oncologists in the treatment of localized rectal adenocarcinoma are accustomed to using capecitabine as a chemosensitizer in patients with localized rectal cancer. If I'm giving chemoradiation for a patient with localized anal cancer, can I substitute the intravenous 5-FU with oral capecitabine? And although the evidence is not as strong in terms of available data with regards to randomized controlled trials, there certainly is data that suggests that capecitabine may be an acceptable alternative in lieu of intravenous 5-fluorouracil that would be given at a dose of 825 milligrams per meter squared on days of radiation. But certainly, I think that that's a feasible approach as well and maybe even associated with less hematologic toxicity than intravenous 5-FU would be.

Brittany Harvey: Great. It's important to understand all the options that are out there for patients with early-stage anal squamous cell carcinoma.

So in addition to those chemoradiation recommendations, what is recommended from the expert panel regarding induction chemotherapy or ongoing adjuvant chemotherapy for this patient population?

Dr. Van Morris: When we think about treating patients with lower GI cancers with curative intent therapies, when we think about the more common rectal adenocarcinoma, oncologists may be used to giving chemoradiation followed by subsequent cytotoxic chemotherapy. But actually when you look at the data for anal cancer, really there's not any data that strongly supports the use of either induction chemotherapy prior to chemoradiation or adjuvant post-chemoradiation chemotherapy. The RTOG 98-11 study was a trial which evaluated the role of induction 5-fluorouracil prior to chemoradiation and did not show any survival benefit or improved outcomes with the use of induction chemotherapy in a randomized control trial setting.

The ACT II trial, which I referenced earlier, was a 2 x 2 design where patients were either randomized to concurrent chemoradiation with 5-FU mitomycin C or concurrent chemoradiation with 5-FU cisplatin. But then there was a second randomization after chemoradiation where half of the study participants received adjuvant cisplatin 5-fluorouracil after completion of their chemo radiation, or the other half were randomized to the standard of care, which of course would be observation. And what that trial showed was that there was no added benefit with the addition of post-chemoradiation cytotoxic chemotherapy. So we look at these data and say that in general, for the general population of patients with localized stages I to III anal cancer, there really is no supporting data suggesting benefit of either induction chemotherapy or adjuvant chemot